Screening for intellectual disability in persons with a substance abuse problem: Exploring the validity of the Hayes Ability Screening Index in a Dutch-speaking sample

There is an increasing interest in screening instruments to detect intellectual disability (ID) in a quick and accurate way in mental health services as well as in the criminal justice system in order to provide appropriate support for people with undetected needs caused by ID. An instrument that has been proven to be useful in both settings is the Hayes Ability Screening Index (HASI). This study assessed the validity of the Dutch version of the HASI in persons with a substance abuse problem residing in mental health services, whether or not mandated to treatment by court order. The HASI was conducted along with the Wechsler Adult Intelligence Scale III as the criterion for validity to 90 participants. Additionally, the influence of psychiatric disorder and medication use on the HASI result was examined. A significant positive relationship was found between the two instruments, demonstrating convergent validity. Using a Receiver Operating Characteristic (ROC) curve analysis, the discriminative ability of the HASI with a cut-off score of 85 was found to be adequate, yielding in a good balance between sensitivity and specificity. The HASI was not distorted by the presence of the substance abuse problem or other psychiatric illnesses and medication did not influence the HASI scores in this study. These findings indicate that the HASI provides a time-efficient and resource-conscious way to detect ID in persons with a substance problem, thus addressing a critical need in mental health settings.